A three-member panel of the U.S. Court of Appeals for the District of Columbia, which after the Supreme Court is the most influential and important American court in matters of regulation and policy, has unanimously upheld the authority of the Environmental Protection Agency to regulate greenhouse gases and declined to second-guess EPA’s timetable for limiting noxious emissions from motor vehicles, power plants, and industrial facilities. The panel said EPA was "unambiguously correct" in claiming authority to regulate greenhouse gas emissions under standing clean air law.

Today's appeals court ruling is notable as much for the force and clarity of its language, as for its substance. The 14 states challenging the EPA's authority argued that EPA had relied on unsound climate science in classing greenhouse gases as pollutants. "The E.P.A. is not required to reprove the existence of the atom every time it approaches a scientific question," said the court, leaving no doubt it considers mainstream climate science essentially credible.

The D.C. appeals panel that issued today's ruling was headed by David B. Sentelle, the court's chief judge, an appointee of Ronald Reagan. The two other members were appointees of Bill Clinton. While the plaintiffs can now appeal the ruling to the full court, it is not obvious that they would fare better with the 13-justice group. To be sure, the court often is sharply critical of regulations and regulators; recently it took the Nuclear Regulatory Commission to task for being too lax in its oversight of nuclear waste management. Then too, the court is known for rigorously and sometimes ruthlessly applying the kind of free-market economic analysis that is near and dear to business-oriented conservatives. At least three members of the court, including Sentelle, have been or are considered potential Republican nominees to the Supreme Court.

Yet, for all that, the character of today's decision strongly suggests the panel is in no doubt about where the court as a whole stands on this issue. A serious environmentalism can be found among conservatives as well as liberals, of course, and respect for scientific consensus is hardly a monopoly of one or the other party. Indeed, the interpretation of EPA's authority enunciated by the D.C. Appeals Court on Tuesday originated in a landmark 2007 decision by a Supreme Court that had essentially the same political balance as today's, despite the retirement and replacement of two justices in the intervening years--that is, a balance that is just slightly tilted to the right.